Matter Modeling Asked by Atom on February 12, 2021
This is a follow-up question to my question posted here. I’ve been trying to study the effects of spin-orbit coupling (SOC) on the band structure of ferromagnetic (FM) material VSe$_{2}$. The input file for the SCF calculation using Quantum ESPRESSO (QE) is given below.
&CONTROL
calculation = 'scf'
outdir = './outdir'
verbosity = 'high'
tprnfor = .true.
tstress = .true.
pseudo_dir = '.'
/
&SYSTEM
ibrav = 0
A = 3.35381
nat = 3
ntyp = 2
ecutwfc = 55
ecutrho = 650
starting_magnetization(1) = 1
starting_magnetization(2) = 0
lspinorb = .true.
noncolin = .true.
occupations = 'smearing'
smearing = 'mv'
degauss = 0.005d0
/
&ELECTRONS
conv_thr = 1e-8
mixing_beta = 0.7d0
/
CELL_PARAMETERS {alat}
1.000000000000000 0.000000000000000 0.000000000000000
-0.500000000000000 0.866025403784439 0.000000000000000
0.000000000000000 0.000000000000000 2.087308375869810
ATOMIC_SPECIES
V 50.94150 V.rel-pbe-spnl-kjpaw_psl.1.0.0.UPF
Se 78.96000 Se.rel-pbe-dn-kjpaw_psl.1.0.0.UPF
ATOMIC_POSITIONS {crystal}
Se 0.666666666666667 0.333333333333333 0.774935000000000
Se 0.333333333333333 0.666666666666667 0.225065000000000
V 0.000000000000000 0.000000000000000 0.000000000000000
K_POINTS {automatic}
6 6 6 0 0 0
This did not converge when I consider the starting_magnetization of Vanadium to be 1 but converges when I assign a starting magnetization of 0 to Vanadium.
And I couldn’t find any example of SOC being considered for Magnetic systems.
So is it necessary to start with a starting_magnetization of zero for magnetic systems while considering SOC?
And I couldn't find any example of SOC being considered for Magnetic systems.
There are many examples that consider the effect of SOC in magnetic systems. For example, the monolayer LaBr$_2$ in this paper, in which the author compares the band structures for three cases as follows:
A bulk case also could be found in this paper: Phys. Rev. Lett. 122, 206401
So is it necessary to start with a starting_magnetization of zero for magnetic systems while considering SOC?
In short, the answer is NO.
The magnetic materials usually are calculated with spin-polarized mode (collinear), in which the electrons are classified into spin-up and spin-down and you only assign the initial magnetic momentum for each atom (just a number).
However, for magnetic materials with heavy atoms, you should do the noncollinear magnetic calculations, in which you should open the tag of SOC and set the initial magnetic momentum for each atom (a $1 times 3$ vector) at the same time.
You may take a look at the explanation about the initial magnetization in vaspwiki.
For QE, you could take a look at the following tutorial to do noncollinear magnetic calculations:
May it helps.
Answered by Jack on February 12, 2021
As a beginner and to the best of my knowledge
Answered by ismail benaicha on February 12, 2021
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